Dresden 2006 – scientific programme

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TT: Tiefe Temperaturen

TT 30: Superconductivity: Twenty Years High-T_c Cuprates - Recent Progress

TT 30.10: Talk

Thursday, March 30, 2006, 16:30–16:45, HSZ 02

Temperature dependent hole distribution in Sr_14−xCa_xCu₂₄O₄₁ — •C. Hess¹, T. Kim¹, M. Knupfer¹, G. Behr¹, B. Büchner¹, N. Nücker², S. Schuppler², P. Nagel², U. Ammerahl³, and A. Revcolevschi³ — ¹IFW Dresden, Institute for Solid State Research, Germany — ²FZ Karlsruhe, Institut für Festkörperphysik — ³Laboratoire de Physico-Chimie des Solides, Université Paris-Sud, France

We studied the effect of charge order in the spin ladder material Sr_14−xCa_xCu₂₄O₄₁ by means of polarization dependent Near-edge x-ray absorption fine structure measurements at the oxygen K-edge (O1s-NEXAFS). Stoichiometry gives a total hole count per formula unit of 6, and the holes are located mainly in the chains although some fraction does dope the ladders as well. At low doping levels a charge ordering transition, which affects the physical properties of both the doped spin chains and spin ladders, is present. We therefore investigated the temperature dependence of the spectra in order to look for a possible redistribution of holes between the different sites (chains and ladders) in the structure, especially at the charge-order transition. From the low temperature spectra we can clearly exclude that the ladder-doping becomes zero as suggested by other experiments. Nevertheless we observe a strong temperature dependence of the spectra.